Manzanita is a challenging shrub to get established.  Soil drainage is the major concern.  They do not require a large amount of water but the timing of when to water is very important.   Good drainage is helpful because it keep the roots from sitting in water for too long. If you do not have good drainage spacing out the watering so the soil can dry out around the root zone is paramount.  Established Manzanita is a great low maintenance shrub with unique beauty.